XWiki as ROOT application doesn't work with URL path based wikis

If I have XEM (1.7.3) running as the ROOT application in Tomcat (webapps/ROOT), and a wiki named "test": the "test" wiki works with xwiki.virtual.usepath=0 at http://test.example.com:8180.

But if xwiki.virtual.usepath=1 and I use http://example.com:8180/xwiki/wiki/test the page layout is messed up and it looks like bits of the wrong skin are applied, and the login page appears embedded within the comments tab. http://example.com:8180/xwiki (the XEM) works fine, though. http://example.com:8180/wiki/test does not work either, it redirects to the XEM login page at http://example.com:8180/bin/login/XWiki/XWikiLogin .

If I change XEM to run as non-ROOT (webapps/xwiki), everything works fine with xwiki.virtual.usepath=1 and http://example.com:8180/xwiki/wiki/test.